There is a technique for dividing data items included in a file stored in a database based on whether the data item is included in a range that is among a plurality of set ranges, and generating a plurality of files. When a search process is to be executed on the database using a certain value as a search criterion, the search process is not executed on a file that is among the plurality of files and for which the set range does not include the value used as the search criterion. Thus, the amount of data to be read for the search process is suppressed.
Even if the files are divided and stored in the database, if a range of values for data included in one of the divided files overlaps a range of values for data included in another one of the divided files, both files are read in the search process. Thus, even though data sizes of the divided and stored files are suppressed, a large amount of data is read for the search process, and the search performance is degraded.